27. Simulation of seismic behavior of a train set

Railway vehicles are connected by couplers and dampers between vehicles. When an earthquake occurs, the varying characteristics of each vehicle and their positions in the train set lead to different earthquake motions. These motions interact with each other, causing each car to behave differently. The effect of this exchange of forces occurring between the vehicles on the derailment as well as the behavior of the vehicles after the derailment was not well understood.

In response to this, we have developed a simulation method for the seismic behavior of a train set that takes into account the effects of coupling (Figure 1).
In this method, individual vehicles are modeled using a combination of multi-body modeling to represent vehicle motion, and finite elements modeling to capture contact phenomena, such as between wheels and rails. By defining the characteristics of springs and dampers that represent the couplings between vehicles, such as dampers between vehicles with attenuation force release functions, it is possible to model the structures to which the vehicles are connected.
Additionally, this method can simulate the series of vehicle behaviors from before to after derailment. It can also represent contact phenomena between track members, such as derailment and deviation countermeasures, and vehicle parts, such as motors, while considering their three-dimensional shapes (Figure 1).
Figure 2 shows an example calculation (sine wave excitation) for a three-vehicle train set using the developed method. While no derailment occurs when all three vehicles are vibrated in the same phase, if the second car vibrates in the opposite phase, an early derailment is observed due to the significant exchange of forces between the vehicles through the coupling structure.
In this method, the calculation of wheel-rail contact during running is partially simplified by omitting creep force calculations to achieve a practical computation speed.

This method can be used as a tool to investigate the causes of derailment accidents during earthquakes under more realistic conditions and to develop measures to prevent derailments and deviations.